One-way gas release valves for maintaining freshness of coffee is known. The valves allow gas pressure within the container to escape, when the pressure is higher than the pressure of the ambient air. However, the holes allowing the valve to function often lead to granulate such as coffee grinds migrating through the venting hole, whereby the valve is rendered ineffective to close against the ambient air.
U.S. Pat. No. 7,527,840 discloses a laminate and a container comprising an integrated pressure release valve. The valve comprises a chamber communicating with the interior of a container through openings provided in a first laminate. A channel is placed between the chamber and an opening provided in a second laminate covering, the chamber and the channel. In the channel, an oil comprising particles is placed. When a pressure arises inside the container, the gas will escape through the first opening, through the first chamber and the channel and out into the atmosphere through the outlet opening. In order to work properly, the opening pressure is high. This has the disadvantage that the containers will balloon before the gas escapes from the containers.